Our passions draw us out into “engagement with the world.” This engagement is not random or according to the whim of the subject, but is already ordered by an apprehension of the good, either sensible or intelligible.
Love is the primary passion toward the good. All other passions in some manner depend on love, insofar as they are ordered to the attainment of what is loved or to the avoidance of what is hated. But hate is itself derivative of what is loved. We hate what is injurious or contrary to what we believe is our good.
An example given is our repugnance toward rotten milk. This repugnance is not simply a preference, but a recognition that such milk is bad. The milk itself has gone bad and is not good for us. There is a correspondence between what we desire and what is good, much of it learned. By nature we pursue what we discover or believe to be good for us.
Our sensible appetite along with our cogitative power (our whole interior sense power) directs us to what we perceive to be a particular good. Through reason, we pursue not just a sensible good, but the good per say.
Steak is sensibly good, but the intelligible good directs me to eat something other than steak for breakfast. While I may persist in thinking steak is an appropriate meal three times a day, I am capable of judging my own judgments. I can take the advice of others and take into account both how I feel as well as my understanding of the purpose of eating and thus make a judgment based not just on this steak here and now and its appeal, but the good of myself as a person (not just a animal or eater).
I can pursue the right act in accord with reason, the act which is ordered both to my physical and spiritual well being. To do this, I must be able to abstract from particular goods and situations to my desire for good and happiness as such. Because no action on my part procures the universal good, I must pursue intermediate ends ordered to the final end.
Despair, hope, love, hate, anger, fear, courage in the passional sense (not the virtues) each contribute to my ability to pursue this end.
When rightly ordered (that is according to reason), these passions direct me toward what is good, away from the evil. Thus there is a variety of modes of engagement by which the human person achieves his rational good, even while the root of this pursuit of happiness (love) is simple.